Drug abuse does not have only a single definition; it has a wide range of definitions that relate to the use of a psychoactive drug or performance enhancing drug in order to achieve a non-therapeutic or non-medical effect. These are in sharp contrast to what we call responsible drug use. Drugs often abused include alcohol, amphetamines, barbiturates, benzodiazepines, cocaine, methaqualone, and opium alkaloids. Other definitions of drug abuse can be classified into four main categories: public health definitions, mass communication and vernacular usage, medical definitions, and political and criminal justice definitions.

The definition of drug abuse by public health practitioners lays more stress on society than the individual. Their definition endeavors to look at the problem from a broader perspective and emphasizes the role of society, culture and availability. Instead of using the terms alcohol or drug "abuse," a number of public health professionals prefer to use terms like "substance and alcohol type problems" or "harmful/problematic use" of drugs.

In British Columbia, the Health Officers Council in 2005 chose to challenge the simplistic black-and-white construction of the binary antonyms "use" vs. "abuse". Instead, their model recognized a spectrum of use, varying from beneficial use to chronic dependence.

In recent times, neither the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders (DSM) nor the World Health Organization's International Statistical Classification of Diseases and Related Health Problems (ICD) recognizes 'drug abuse' as a medical diagnosis. The DSM has opted for the term